Written by Calvin on July 30, 2014 /Calvin’s Corner
Wheel Tension App Overview
Wheel truing can be big playfulness. It provides us chance to focus on something that should be dim-witted, something that bends to our will, so to speak. Get a cup of dear chocolate, sit yourself in front of a true stand, and chew over on making a perfect bicycle ( number 1 ).
figure 1. Some calculator interfacing can make you a better automobile mechanic
There are of course many tools that can help you make better wheels. Truing stands, spoke wrenches, dishing tools, and a Park Tool TM-1 Tension Meter will make things go right. With the TM-1, you can know the stringency of the spokes overall ( modal spoke tension ) deoxyadenosine monophosphate well as know the relative talk tension ( how nasty each speak is relative to the other spokes in the rack ).
Reading: Wheel Tension App Overview
Wheel Tension Balance Web App
This article will address the practice of a new and completely free joyride, namely the Wheel Tension App. The WTA app is designed to provide backing and support to the TM-1. This web app provides you an easy and firm way to convert your wheel ’ s TM-1 readings into a kgf read. additionally, the WTA provides a ocular diagram of the relative talk latent hostility using a “ radar chart ” ( figure 2 ) .
number 2. The WTA used on a 20 spoke rear wheel
If you have never used a TM-1 Tension Meter before, this tool basically flexes a wheel rundle between steel studs using a calibrate spring. A scale gives you a read of the amount the spoke deflects. This deflection understand is correlated to, but is not the same thing as, the violence pull or tensioning the speak. See more of the TM-1 use at Wheel Tension Measurement .
To know the measure of force, you use the chart that comes with the tool. unlike diameter spokes will have different read for the same sum of pulling wedge. then to know the tension on an entire bicycle means lots of writing things down from column, and then adding them up and separate .
Any mathematics is excessively much mathematics for most people. But now, we have the WTA to do all that figuring for you. The concept of this app is based on an Excel spreadsheet once offered in previous Calvin ’ south Corner, here at the Park Tool web site. This earlier attempt required downloading a file and running it off your intemperate driveway. The file contained what are called “ macro, ” and it became impossible to keep up with all the changes in calculator operating systems. We abandoned that adaptation in favor of the WTA .
This updated and improved WTA is much cleaner and easier to use compared to the previous adaptation. The WTA app besides features a nice amobarbital sodium button called Instructions. Find it. Click it. Read it. This page will focus on why to used this network app. See the “ how ” to use the WTA at the a fore mentioned blue button .
It is authoritative to understand what the WTA is showing you. This app does not graph out the “ truth ” or run-out of the wheel flange. In fact, when learning how to use the WTA, the wheel should be running heterosexual and round. What the WTA does is organize the TM-1 data on wheel spoke tension into a functional format .
Although personally I find it very entertain, you do not in truth need to measure the talk tension of every bicycle you see. There are however some good reasons you may want to use the WTA. For the base machinist, new to working on wheels and truing wheels, it can help make sense of what is going on with a wheel. It will help build confidence .
For professional mechanics and wheel builders, it can provide confirmation you have produced a good wheel. additionally, it provides you can give to the customer. When correctly used, this data can provide a deeper understanding of what is going on, merely like game stats provide a deeper understanding of a baseball game .
Improving Your Wheel Work With Data
With some practice, many people can true ( straighten ) a wheel spinning so it will not strike the frame or rim caliper bracken pads. Spoke nipples are turned to move sections of the rim left or correct as needed. When the roulette wheel looks like it is not wobbling and spins straight, most people will sit back and admire their handicraft. Done, finished, let ’ s depend on .
But delay, there ’ randomness more ! We can take that wheel and make it better. however, to understand how we need to review some wheel theory .
When we ride, we are stressing the rack rim and spokes. Just riding along, as is said, will cause a change in talk tension every time that wheel goes around. therefore consider riding only one sea mile. Your spokes are seeing 745 revolutions on a typical bicycle wheel ( 465 per kilometer ). nowadays consider your afternoon drive, that ’ s like, well, you do the mathematics. We can say each speak gets stressed a bunch for a season of riding .
To keep the wheel spinning nicely for a longer time and over all sorts of terrain, it is best to balance the speak tension. many novitiate mechanics ( and not-so-novice ) assume that when the wheel is running without careen left to right, the spokes must be all the lapp relative tension. That is simply not discipline .
Why is that ? even a brand fresh roulette wheel and even with good choice rims, the wheel builder or machinist can unwittingly produce a bicycle that spins straight, but the spokes are quite different in tension, some being tighter and some loose. This is something that we can improve. We call this “ balancing ” the tension. however, first understand that spokes are balanced to other same-side spokes. We would like to have left side spokes relatively close in tension to all left side spoke, and all correct side spokes stopping point in latent hostility to right side spokes. You will have tension imbalances when one speak is pulled nasty while neighboring same-side spokes are relatively loose. ideally, we want a site of “ sharing the load, ” with all spokes pulling their weight, more or less, evenly .
Why this desire for relative even spoke tension ( balancing ) ? A talk that is looser relative to its neighbors will tend to loosen even more during habit, and this will result in the rack coming out of true. however, spokes that are excessively taut can stress the rim, and this can result in a crack up at the nipple hole. Wheels with even spoke latent hostility will stay true longer, and as a bonus, your speak life will be maximized .
Have a look at the example below in Figure 3. It is a 24-hole rear rack, with a light rim. For this user, we are trying to hold close balance tolerances, so we selected the asset or minus 10 % option. The spokes are tightly, but there is a balance issue on the right side at the fourth rundle, counting from the valve hole. Spoke # 4 is besides close, and spoke # 5 is besides loose. We are trying to transfer some of the static load of # 4 over to # 5. The idea here is to loosen # 4 a bit. however, precisely loosening # 4 will cause the wheel to come out of true, so we must besides tighten # 5 to pull it binding straight .
figure 3. A 24-hole rear bicycle that could use tension balancing
On the left side of this same bicycle, we have two places that are out our hope tolerance. Spoke # 4 will need tension transferred to # 5. then on the leave, spoke # 7 will need relax. This must be offset by tightening possibly # 6 or # 8, or possibly a little of each. The idea is to maintain good true, but achieve balanced and even tension while you do this .
WARNING : a entertaining as the WTA is, remember we need to finally go tease the bicycle. For the professional, you must give back the customers ’ bicycle. It will never be perfect, and it doesn ’ t need to be. Keep in heed that rim hoops are made from roll aluminum extrusions. A straight nibble of metal is pushed through rollers to bend it in a lap. It is then joined by pins or by welding. The hoop ends up with internal stress even before the spokes are put in to the hub. Carbon Fiber rims besides are not made absolutely. You much have a deal off between a nicely balanced address tension, and a absolutely straight spinning wheel .
To have a better grok of why this rundle latent hostility reconciliation is a dear thing to do, let ’ s have a front at a common wheel stresses. Below we will review Radial Loads, Torsional Loads at the hub, and Air Pressure. Just plain old smashing the roulette wheel will be covered concluding .
visualize 4. Rear wheel under radial load
Read more: Freewheel Removal and Installation
Effect of Radial Load
Rims get a down load at the hub precisely by sitting on the bicycle and ride. This stress tends to flatten the rim slightly at the bottom, close to the 6:00 place. Because of this flatten, the bottom few spokes will drop slightly in tension. however, at the same time, the spokes to the bequeath and correct slope of the bed, at the 3:00 and 9:00 positions, advance slightly in tension. The spokes at the 12:00 position do not gain latent hostility ( name 4 ) .
Remember, every time the rack rotates, each talk goes through this cycle of getting lax and mean. This tease impression of merely riding is an example of why poise is useful for the wheel. Like all fasteners, the leaning is that a loose bang and nut will get even looser during the stress of habit. If a address were relatively loosen compared to early spokes, this talk will then get even looser as you roll along .
figure 5. Radar graph illustrating the effect of a torsionally rotated rear hub
Effect of Torsion Applied at Hub
When we ride, the chain pulls on the rear cogs and this rotates the rear hub, which moves the spokes, and finally all this rotates the flange and tire. This twist or rotational force at the hub is transmitted through the spokes. Most wheels are laced with “ tangent spoking, ” where they leave the hub at an slant. Spoke radiating to the back are called “ trailing ” or “ pulling spokes. ” Spokes radiating ahead are “ leading ” or “ pushing spokes. ” When the hub is twisted during bicycle, it pulls on the “ pulling ” spokes and besides relieves tension on the “ pushing ” spokes. The resulting WTA radar chart takes on a headliner supreme headquarters allied powers europe when this is measured ( figure 5 ) .
The points of the headliner form in figure 5 are the pull spokes, which jumped up in tension. The in points are the pushing spokes, showing a drop in tension. The hard you push the cranks, the more dramatic the effect. Remember this happen doubly per grouch revolution, once for each office accident .
A similar tortuosity or twisting load is applied through the spokes by rotor magnetic disk brake. The load and stress on spokes from a rotor disk during brake can be much greater compared to the try of pedal. The rim caliper brakes, however, do not apply braking force out through the spokes in the like way .
Effect of Air Pressure
There is another force acting on rims we may not think about. inflate tires squeeze the flange and this can slightly lower the overall speak tension. The effect is more hard if rim is light weight with a specialize profile and the tire is run at high press. In name 6, a light weight road wheel is shown with and without bore atmospheric pressure. The tension pattern is basically the same, but there is a little decrease in overall tension. The MTB wheels are typically run lower blackmail and there is identical short latent hostility decrease. besides, on cryptic sidewall rims, there is less of this effects because they are more rigid in the direction of stress .
Do not, however, add extra latent hostility beyond normal manufacturer ’ s recommendations to account this drop curtain. This effect if being discussed only to show you there are several things acting to lower your wheel tension as you ride .
figure 6. The lapp wheel shown with and without tire pressure
Diagnostic Use of the WTA
The WTA can besides be useful when diagnosing rim and wheel problems. In these cases you may want to begin by running the numbers on the WTA before grabbing a address twist. View the chart as you inspect the rim drift. The wobble or run out along with the WTA will tell you a fib of what has happened to this wheel .
Take for example the rear wheel below that was badly out of true ( human body 7 ), wobbling back and forth closely 1/2″ ( 12mm ). The WTA on this wheel shows some problems. however, inspecting the flange movement of the rim combined with the changes in proportional talk tension tells us this rim has been flex. The rim was moving to the leave at talk # 5.This department of rim needs to be moved bet on to the mighty. normally, tightening the right speak # 5 would help accomplish this, as would loosening left side spoke # 5. But check the WTA graph. right side # 5 is already identical close, and left side # 5 is loose. Adjusting these spokes are very improbable to help at all. This section of rim has been bent, deformed credibly by impact .
however, not all wheels that shimmy have a bent brim. The phonograph record wheel below was again a rise bicycle, and about 1/2″ ( 12mm ) lateral runout ( human body 8 ). The WTA chart looks atrocious at first glance. however, it is necessity to consider the localization and commission of the shimmy. The flange pulls toward the left at address # 2. however, notice that left side spoke # 2 is besides spiked in latent hostility. It makes sense it would move entrust. then the rim moves toward the correct at spoke # 6, and then left at # 9, and then right again at # 10. The rim movements match what we expect with the rundle tension chart. Loosen up this entire roulette wheel and begin over with tied tension. The rim hoop is credibly finely, it fair needs some attention .
design 7. Rear wheel with bent rim
calculate 8. Disc wheel in need of TLC
Broken Spoke and Tension Balance
With enough use and depend on, spokes can finally fail and break. This can occur from stress fatigue. Going around and around excessively many times under load just takes it out of a talk. Or, a address can break from a derailleur or stick getting in the wheel ( regarding the former, please double check your limit screw settings ). When one spoke fails it will affect the entire wheel to some academic degree. The area of brim at the talk failure will come out of true and move laterally as the spoke is nowadays effectively at 0 kgf. figure 9 below illustrates break right side spoke at # 9, now at 0 kgf. This wheel was primitively well balanced. The two neighbor spokes, right side # 10 and right side # 8, went up in tension because there was no longer pulling at correct side # 9. however, the entire right english tension has changed, showing an ovalizing of the radiation pattern, with tension increasing opposite the breakage. Corresponding to this effect is the ovalizing of the left slope, but it is at a 90-degree offset. The leave address right at the area of right side # 8 rose in tension because the rim is besides now pulling away from the hub. The roulette wheel pulls to the leave at the area of speak # 8, but besides pulls to the veracious at correct spoke # 16, which have increased in latent hostility as a result of the interrupt # 8. Put in a new talk, and pull it up to the average tension, then very well tune the wheel .
human body 9. Wheel tension from broken speak # 8 on the right side
trope 10. radial brim disfigurement and damage at spokes # 8 and # 9
Radial Rim Damage and Tension Balance
A slight total of rim flex and distortion are common just from the weight of the cyclist. however, when you see a rim that has struck something head-on, such as a bridle, road pothole, or most anything solid, it can deform and bend the rim. In this sheath the hoop will show a “ flat spot, ” where the rim drops radially toward the hub. here, the WTA shows lower tension on both the leave and right side in flatted area ( figure 10 ). If the hoop was is good condition, we would expect this department to be a “ high gear spot, ” with this department of rim pulling aside from the hub. We might at foremost think we can fix this damaged flange by loosening these spokes in the effect area. But the spokes are already relatively low there, and loosening further is unlikely to have any effect. The rim metallic element is bend and spoke tension can not push the hoop back into form .
Folded Wheels and Tension Balance
If the brim has experienced a major lateral impingement, it may fold or “ greaser, ” taking the form ( slightly ) of a hard shell greaser. This is bad for the rider and bicycle owner, but it does provide an interesting phenomenon in tension ( figure 11 ). There is a similar form on each slope, but offset by 90 degrees. properly side spokes # 2, # 3. # 4, and then # 11, # 12, and # 13 are tight. however, away from these spokes the tension promptly falls off, with spokes # 6, # 7, # 8, # 9, and then # 15, # 16, and # 17 efficaciously 0 kgf. The traffic pattern repeats on the leave side, but here the tight spokes are # 16, # 17, # 18, and then # 7, # 8 and # 9 .
design 11. The pen up or “ taco ” rim convention, not a “ golden four-leaf clover ” for the rider
figure 12. The same tacoed wheel as figure 8 after “ re-bending ” and repairing by truing
Read more: HEXCENTRIX
It is claimed by some people that this “ greaser ” can be fixed by re-bending the wheel. Well, you can try to re-bend it all you want, but you will not be returning the wicket back to its original human body. There is limited degree of “ repairability ” here, but this normally leads to dreadfully unbalance spoke tension. The wheel will appear “ available ” for a while but it will not hold it shape for long. The wheel from figure 11 was pushed and re-bent back into human body. After the re-bending, the wheel was approximately 7mm out of lateral true, which was unacceptable for habit. With more corrections by truing and using rundle latent hostility, the lateral true was improved to about 1mm lateral erroneousness, good adequate to for coarse casual practice. Although we might have thought we fixed this for our friend, this wheel will not be staying straight very long. The WTA graph shows the history .
The WTA is a system for you to manually record talk tension. It provides Kilogram military unit ( kgf ) reading easier than using the chart that comes with the TM-1. The WTA will organize your TM-1 measurements into a useful format. With some learning on your region, the WTA can get you a better admiration and agreement of what is going on tension wise in your wheels. Take the time to crunch the numbers .